1. Field of the Invention
The present invention relates to an implantable cardiac stimulating device of the type having a housing, a control circuit enclosed in the housing, the control circuit being adapted for connection to a first electrode positioned to stimulate a first ventricle of the heart and to a second electrode positioned to stimulate the second ventricle of the heart, and wherein control circuit controls the delivery of stimulating pulses to the first and second electrodes, and means for sensing at least one evoked response parameter to the stimulation of the first and second ventricles.
2. Description of the Prior Art
Most pacers are arranged to stimulate the right ventricle of the heart, but it is also known to stimulate the left ventricle. In particular for the treatment of congestive heart failure or other severe cardiac failures it is known to stimulate the left ventricle, or both ventricles, in order to optimize the hemodynamic performance of the heart.
U.S. Pat. No. 5,728,140 describes a method and an apparatus for pacing the left ventricle of the heart. The pacing electrode is positioned within the interventricular septum proximate the left ventricular wall thereof.
United States Patent No. describes different possible electrode positions in order to stimulate or sense the different chambers of the heart.
Also the article “A Method for Permanent Transvenous Left Ventricular Pacing” by Blanc et al, PACE, Vol. 21, 1998, pp. 2021-2024, describes a method for positioning leads for left ventricular pacing.
U.S. Pat. No. 4,928,688 describes a method and an apparatus for treating patients suffering from congestive heart failure by stimulating both the ventricles. The document discusses the problem involved when the left and right ventricles contract asynchronously. In order to effect substantially simultaneous contraction of both ventricles, the document suggests means for separately processing sensed cardiac signals from each of the right and left ventricles. If ventricular contractions are not sensed in both ventricles within a period of coincidence defined by a time delay, the pacing pulse will be emitted at the end of this time delay, but only to the ventricle for which a QRS-complex has not been sensed. The time delay is suggested to be in the order of 5-10 ms.